Nuts having an internal thread with a wedge ramp at the root thereof, of the type disclosed in U.S. Pat. No. 4,076,064, are often used in combination with standard bolts to enhance the ability of the nut and bolt assembly to maintain its integrity in vibratory environments. However, the nature of the wedge ramp is such that reduction of axial load on the nut and bolt assembly below a predetermined level, caused by, for example, thermal expansion and lengthening of the bolt, may induce loosening. This problem may be solved by insuring that a minimum axial load or "preload" is maintained on the nut and bolt assembly.